1. Field of the Invention
The present invention relates to a lighting apparatus using a plane light source represented by, for example, an organic EL (electroluminescence) element.
2. Description of the Related Art
Since an organic EL element is driven by a low DC voltage, it has a high luminous efficiency and can be reduced in weight and thinned, as well as it has a feature that it generates substantially no heat. Therefore, it is used for a flat panel display (FPD) in some portable devices etc. By employing the element as a plane light source, it is also arranged to be used as, for example, a back light of a liquid crystal display element.
Further, by selection of a material used for an EL luminescence layer, the above-mentioned organic EL element may provide luminescence colors of R (red), G (green), B (blue), or others. Therefore, by using each of the above-mentioned luminescence colors independently or combining a plurality of types of luminescence colors, white or near white luminescence color may be obtained. Thus, by constructing the organic EL element as the plane light source (light emitting panel), it can be used as the light source for decoration and an efficient light source which illuminates the interior of a room etc.
Japanese Patent Application Publication No. 2007-173424 discloses a ceiling-mounted lighting apparatus in which the above-mentioned organic EL element is formed as a circular or ring-shaped plane light emitter.
Incidentally, according to the lighting apparatus as disclosed in Japanese Patent Application Publication No. 2007-173424, it aims to providing a lighting apparatus which omits an outer frame and emits light to an edge, taking advantage of the feature of the above-mentioned organic EL element.
For this reason, an engaging portion to be engaged with a ceiling hook attached to the ceiling is provided in the central portion of the lighting apparatus. Further, Japanese Patent Application Publication No. 2007-173424 discloses that a light emitting unit having the organic EL element formed in the shape of a ring may be in the shape of a single ring or may be divided into a plurality narrow rings, and that the light emitting unit may be formed so as to further extend radially from the center.
However, in the above-mentioned lighting apparatus, it only suggests that a luminescence pattern in a flat luminescence surface is devised, and it has no distinctions, lacks a cubic effect, and remains monotonous in the devised range of the above-mentioned luminescence pattern. Therefore, it is impossible to allow the illumination to give a gorgeous stage effect etc.